The influence of three commercial diets with different protein and lipid contents (40\ :\ 14, 45\ :\ 8, 48\ :\ 8 protein\ :\ lipid {\textendash} P\ :\ L, in \% dry weight of diet) on growth performance, survival and the histology of the liver and intestine was analysed in early juveniles of silver arowana, Osteoglossum\ bicirrhosum, reared in captivity. Individuals (initial wet\ weight{\textendash}Wi\ =\ 1.07\ {\textpm}\ 0.04\ g; total length{\textendash}TL\ = 6.0\ {\textpm} 0.17\ cm) were raised in triplicate (n\ =\ 12 fish per tank) at 26.2\ {\textpm}\ 0.1{\textdegree}C and fed one of three commercial diets over 60\ days. At the end of the trial, survival (90.5\ {\textpm}\ 3.3\%) and condition factor (0.5\ {\textpm}\ 0.02) were not affected by dietary treatments, whereas specific growth rate, TL and W gain were lower in animals fed the 40P\ :\ 14L diet. Histological analysis revealed a larger accumulation of lipid droplets in the intestines of the group supplied with the 40P\ :\ 14L diet, as well as a larger surface of hepatic lipid vacuoles compared to the other treatments, although no signs of steatosis were observed. Juveniles fed the 48P\ :\ 8L diet displayed the lowest liver lipid accumulation; however, a protein content higher than 45\% did not improve growth performance. The intestine and liver lipid accumulation of individuals fed the 45P\ :\ 8L diet might indicate a more balanced lipidic metabolism. Intestine and liver histologies proved to be useful markers to identify the nutritional condition in juveniles of O.\ bicirrhosum, even when differences in nutritional composition were subtle (i.e. protein variation of 3\%).

The aim of the study was to evaluate the influence of different dietary protein and lipid levels and their ratios on larval growth, survival and the incidence of cannibalism in Pseudoplatystoma punctifer. Larvae were raised in a recirculation system from 3 to 26\ days post-fertilization (dpf) (2{\textendash}25\ days post hatching, dph) at an initial density of 40 larvae L-1, 27.8\ {\textpm}\ 0.65{\textdegree}C and 0L\ :\ 24D photoperiod. Larvae were fed from 4 to 12 dpf with Artemia nauplii and weaned onto four different compound diets from 13 dpf within 3\ days, then fed exclusively with these diets until 26 dpf. These diets contained 30\ :\ 15, 30\ :\ 10, 45\ :\ 15 or 45\ :\ 10 protein\ :\ lipid (P\ :\ L) (in \% of dry matter) levels. A control group was fed Artemia nauplii until 17 dpf and weaned thereafter with the 45P\ :\ 10L compound diet. The experiment was carried out in triplicate. Results showed higher growth and survival rates and lower incidence of cannibalism in the group fed the 45P\ :\ 15L diet than in the other treatments. Differences in larval survival and growth performance were associated with the higher protein and lipid content rather than the protein\ :\ lipid ratio of this diet. When comparing diets with the same protein level, the increase in dietary lipid led to an improvement in growth, suggesting that energy from lipids spares protein for growth in P.\ punctifer fingerlings. An Artemia feeding period longer than 12 dpf did not improve larval growth or survival.

The diversity of sponge-associated fungi has been poorly investigated in remote geographical areas like Antarctica. In this study, 101 phenotypically different fungal isolates were obtained from 11 sponge samples collected in King George Island, Antarctica. The analysis of ITS sequences revealed that they belong to the phylum Ascomycota. Sixty-five isolates belong to the genera Geomyces, Penicillium, Epicoccum, Pseudeurotium, Thelebolus, Cladosporium, Aspergillus, Aureobasidium, Phoma, and Trichocladium but 36 isolates could not be identified at genus level. In order to estimate the potential of these isolates as producers of interesting bioactivities, antimicrobial, antitumoral and antioxidant activities of fungal culture extracts were assayed. Around 51\% of the extracts, mainly from the genus Geomyces and non identified relatives, showed antimicrobial activity against some of the bacteria tested. On the other hand, around 42\% of the extracts showed potent antitumoral activity, Geomyces sp. having the best performance. Finally, the potential of the isolated fungi as producers of antioxidant activity seems to be moderate. Our results suggest that fungi associated with Antarctic sponges, particularly Geomyces, would be valuable sources of antimicrobial and antitumoral compounds. To our knowledge, this is the first report describing the biodiversity and the metabolic potential of fungi associated with Antarctic marine sponges.

Fish tissues, particularly rich in n-3 PUFA, are prone to lipid peroxidation that can damage cellular membranes, cause severe lesions and subsequently incidences of disease and mortality. However, fish possess antioxidant defences, such as vitamin E (VE) and antioxidant enzymes, to protect them against oxidative damage. This study investigated the effects of an increasing gradient of oxidized dietary lipid on the survival, growth performance, skeletogenesis and antioxidant defensive processes occurring in Senegalese sole (Solea senegalensis) larvae. Four groups of fish were fed live prey enriched with experimental emulsions containing an increasing gradient of oxidized oil: non-oxidized, NO+VE, 34.5\ nmol MDA g-1 w.w.; mildly oxidized, MO+VE, 43.1\ nmol MDA g-1 w.w.; highly oxidized, HO+VE, 63.3\ nmol MDA g-1 w.w. and highly oxidized without VE, HO-VE, 78.8\ nmol MDA g-1 w.w. The oxidation levels increased in enriched rotifers following the oxidation gradient of the emulsions, but were not affected in enriched Artemia metanauplii. The oxidation status of Senegalese sole larvae increased during development, but this was not related to the dietary treatments. The increasing dietary oxidation levels did not affect the fatty acid profile, survival, growth performance and metamorphosis processes of sole larvae. Senegalese sole seem to activate antioxidant defence mechanisms in response to the increasing amounts of dietary peroxidized lipids, in a manner efficiently enough to prevent detection of any alterations of these physiological processes. Antioxidant systems and detoxification mechanisms appeared to occur through the consumption of dietary α-tocopherol, the activation of the antioxidant enzymes (catalase, superoxide dismutase, glutathione S-transferase, glutathione reductase) and the retention of oxidized fat in the intestinal enterocytes for detoxification prior to their utilization. However, fish fed the highest oxidized diet presented a reduction in bone mineralization, but lower incidence of deformities in the vertebral and caudal regions than fish fed the other diets. This study exemplifies the importance of rearing Senegalese sole larvae on non-oxidized diets during the early larval development to avoid detrimental consequences in older fish, most notably in the process of skeletogenesis.

Flatfish can provide a reliable model to study developmental disorders in bone tissues occurring during morphogenesis in response to nutritional imbalances. To date, most studies dealing with the effect of dietary essential fatty acids (EFA) on skeletogenesis in fish have focused their investigation on the role of docohexanoic (22:6n-3, DHA) and eicosapentaenoic (20:5n{\textendash}3, EPA) acids, but only a few have focused on investigating the effects of arachidonic acid (20:4n{\textendash}6, ARA) on bone during fish larval development. Bone development and composition at larval stage have been demonstrated to be highly sensitive to dietary levels of EFA, in particular the EPA and ARA acids, both precursors for highly bioactive eicosanoids presenting opposite effects on bone metabolism. Since fish are not able to synthesize EFA, they need to obtain them from the diet. However, dietary imbalances in EPA and ARA in flatfish larvae may disrupt bone formation and osteoblast differentiation in skeletal tissues, leading to the incidence of skeletal deformities, reduced mineralization and problems of bone remodelling in the cranial region associated with impaired eye migration. These anomalies in skeletal structures are one of the most important factors that affect flatfish larval quality and hamper their production. Thus, we have reviewed the current state of knowledge about the effects of dietary ARA contents on skeletogenesis in Senegalese sole (Solea senegalensis), one of the main flatfish species cultured in Europe. Their larval quality still suffers for a high incidence of skeletal anomalies induced by dietary imbalances during metamorphosis.

Abstract In this study we evaluated the effects of high dietary arachidonic acid (ARA) levels on prostaglandin \{E2\} (PGE2) and \{E3\} (PGE3) production and their effect on two morphogenetic processes occurring during metamorphosis: the establishment of the juvenile pigmentation pattern and eye migration and remodeling of cranial bones. In this sense, Senegalese sole larvae were fed from 2 to 50 days post-hatch (dph) with live prey enriched with an experimental emulsion containing high levels of \{ARA\} (ARA-H; 10.2 and 7.1\% \{TFA\} in enriched rotifer and Artemia, respectively) versus a reference commercial enriching product (Algamac 3050{\textregistered}, AGM; 1.0 and 1.4\% \{TFA\} in enriched rotifer and Artemia, respectively). High dietary \{ARA\} levels did not affect larval growth performance at 50 dph, but significantly induced malpigmentation (81.4 {\textpm} 7.5\%, versus 0.9 {\textpm} 0.3\% in larvae fed the \{AGM\} diet). This malpigmentation was linked to the higher prostaglandin \{E2\} (PGE2) levels observed in pseudo-albino fish as compared to normally pigmented individuals. The \{PGE2\} levels were higher in normally pigmented specimens fed the ARA-H diet than in those fed the \{AGM\} diet. The effects of \{ARA\} on normally pigmented fish fed the \{AGM\} diet and pseudo-albino specimens fed the ARA-H diet were evaluated by means of the density of melanophores and the texture and image segmentation analyses in the dorsal skin of post-metamorphic fish. The skin of pseudo-albino specimens had a more uniform and homogeneous melanophore pattern than normally pigmented fish. Melanophores in pseudo-albino specimens were less abundant and not so aggregated in patches as they were in normally pigmented ones, whereas their shape differed (round vs. dendritic) suggesting their inability to disperse melanin. In addition, fish fed the ARA-H diet presented a higher percentage of cranial deformities (95.1 {\textpm} 1.5\%) than those fed the control diet (1.9 {\textpm} 1.9\%) that was significantly and negatively correlated with the incidence of normally-pigmented animals (R2 = - 0.88, P \< 0.001). Cranial deformities in pseudo-albino fish were associated with an impaired migration of the eye from the ocular side (the right eye), whereas the left eye migrated from the blind side into the ocular side almost normally. The effects of high dietary \{ARA\} levels in the eye migration and cranial bone remodeling processes in post-metamorphic larvae were evaluated by means of the staining of cranial skeletal elements. Pseudo-albino fish showed higher interocular distance and head height than normally pigmented individuals, a different disposition of the eyes with regard to the vertebral column and mouth axes, and a distinct osteological development of some skeletal structures from the neuro- and splanchnocranium, in relation to high dietary \{ARA\} contents and high \{PGE2\} production. These results brought new information about possible nutritional forcing factors and physiological mechanisms of pigmentary disorders and impaired eye migration, which are current major bottlenecks in flatfish aquaculture.

The organogenesis of the digestive system was described in the Amazonian pimelodid catfish species Pseudoplatystoma punctifer from hatching (3.5 mm total length, TL) to 41 days post-fertilization (dpf) (58.1 mm TL) reared at 28{\textdegree}C. Newly hatched larvae showed a simple digestive tract, which appeared as a straight undifferentiated and unfolded tube lined by a single layer of columnar epithelial cells (future enterocytes). During the endogenous feeding period, comprised between 20 and 96 h post-fertilization (3.5 to 6.1 mm TL), the larval digestive system experienced a fast transformation with the almost complete development and differentiation of most of digestive organs (buccopahrynx, oesophagus, intestine, liver and exocrine pancreas). Yolk reserves were not completely depleted at the onset of exogenous feeding (4 dpf, 6.1 mm TL), and a period of mixed nutrition was observed up to 6 to 7 dpf (6.8 to 7.3 mm TL) when yolk was definitively exhausted. The stomach was the organ that latest achieved its complete differentiation, characterized by the development of abundant gastric glands in the fundic stomach between 10 and 15 dpf (10.9 to 15.8 mm TL) and the formation of the pyloric sphincter at the junction of the pyloric stomach and the anterior intestine at 15 dpf (15.8 mm TL). The above-mentioned morphological and histological features observed suggested the achievement of a digestive system characteristic of P. punctifer juveniles and adults. The ontogeny of the digestive system in P. punctifer followed the same general pattern as in most Siluriform species so far, although some species-specific differences in the timing of differentiation of several digestive structures were noted, which might be related to different reproductive guilds, egg and larval size or even different larval rearing practices. According to present findings on the histological development of the digestive system in P. punctifer, some recommendations regarding the rearing practices of this species are also provided in order to improve the actual larval rearing techniques of this fast-growing Neotropical catfish species.

A prototype of an integrated closed system for fish-plankton aquaculture was developed in Iquitos (Peruvian Amazonia) in order to cultivate the Tiger Catfish, Pseudoplatystoma punctifer (Castelnau, 1855). This freshwater recirculating system consisted of two linked sewage tanks with an intensive rearing unit (a cage) for P. punctifer placed in the first, and with a fish-plankton trophic chain replacing the filters commonly used in clear water closed systems. Detritivorous and zooplanktivorous fishes (Loricariidae and Cichlidae), maintained without external feeding in the sewage volume, mineralized organic matter and permitted the stabilization of the phytoplankton biomass. Water exchange and organic waste discharge were not necessary. In this paper we describe the processes undertaken to equilibrate this ecosystem: first the elimination of an un-adapted spiny alga, Golenkinia sp., whose proliferation was favored by the presence of a small rotifer, Trichocerca sp., and second the control of this rotifer proliferation via the introduction of two cichlid species, Acaronia nassa Heckel, 1840 and Satanoperca jurupari Heckel, 1840, in the sewage part. This favored some development of the green algae Nannochloris sp. and Chlorella sp. At that time we took the opportunity to begin a 3-month rearing test of P. punctifer. The mean specific growth rate and feed conversion ratio (FCR) of P. punctifer were 1.43 and 1.27, respectively, and the global FCR, including fish in the sewage part, was 1.08. This system has proven to be suitable for growing P. punctifer juveniles out to adult, and provides several practical advantages compared with traditional recirculating clear water systems, which use a combination of mechanical and biological filters and require periodic waste removal, leading to water and organic matter losses.

Abstract High dietary levels of arachidonic acid (ARA) and its relative proportions with eicosapentaenoic acid (EPA), fed during early larval stages, have been associated with malpigmentation in various flatfish species. This study investigated whether the nutritional induction of pigmentary disorders at larval stages was related to a specific larval period of increased sensitivity to \{ARA\} in Senegalese sole (Solea senegalensis Kaup, 1858). Senegalese sole larvae were fed high dietary \{ARA\} levels during pre- and pro-metamorphosis (2{\textendash}15 dph) and/or post-metamorphosis (15{\textendash}50 dph). Larval tissues reflected the dietary fatty acid composition. Malpigmentations were significantly related to elevated dietary and larval \{ARA\} contents and ARA/EPA ratio. This study reports evidence for a {\textquotedblleft}pigmentation window{\textquotedblright}, with a higher larval sensitivity to dietary \{ARA\} during pre- and pro-metamorphosis than post-metamorphosis. High dietary \{ARA\} fed to larvae during pre-metamorphosis enhanced survival, but did not affect growth nor eye migration. The aspect and density of melanophores in the skin of the ocular side of ARA-induced pseudo-albinos were significantly reduced in comparison to normally pigmented individuals, even more in the pseudo-albino fish fed high dietary \{ARA\} levels during the pre-metamorphic stage. Pseudo-albino fish fed high dietary \{ARA\} levels during post-metamorphosis showed higher concentrations of 2- and 3-series prostaglandins (PGE2 and PGE3) than normally pigmented specimens fed the same diets. An increased sensitivity to ARA-induced malpigmentations has been identified at pre-metamorphosis and early metamorphosis in Senegalese sole. Supplying high dietary \{ARA\} amounts imbalanced the dietary ARA/EPA ratio and disrupted the relative concentrations of derived \{PGE2\} and PGE3, resulting in 20 to 81.7\% pseudo-albino individuals, depending on the dietary treatment. The administration of high levels of dietary \{ARA\} at different developmental stages did not only affect the incidence of animals with pigmentary disorders, but it also affect the melanophore density and skin aspect in normally pigmented and pseudoalbino fish as image segmentation and texture analyses indicated.